The answer to this question is partly semantics so we have to clear up the definitions first. Progressive thinking is associated with the Progressive Movement which operated from 1870–1940. Those Progressives agitated to reverse worker exploitation and corrupt politics. They were successful in that endeavor.
American Liberalism did not appear until after World War II. President Truman made opposition to communism a key component of his administration. That decision isolated the Progressives because they had been traditionally against foreign intervention. The actually ran Henry Wallace as a Progressive candidate against Truman in 1948. When Truman won, Liberals took control of the party and the Progressives became marginalized until the 1960s.
I say American Liberalism because, as at least one other person pointed out, it was very different that the European version we call “Classic” Liberalism.
American Liberalism prospered until the early seventies, when it got a bad name over the failure of the welfare system. That is what I think you mean by “ashamed”. Today’s Liberals do not want to be associated with big government programs that do not work and waste money.
As Liberalism waned, the Progressives rose again, starting during the George W. Bush administration.
Progressives sit to the left of Liberals in the Democratic Party. They are more aggressive about wanting change even to the point of changing the government. They are very sensitive to the poor and other disadvantaged groups and they hate capitalism as exploitative.